Sorry I posted also on Melabs forum, hopeing to quicker reads comments:

I started to have unexpected behaviours in my program with a PIC18F67K22 (128k).
After some days of debugging I finally discovered that troubles happens when I call a piece of code that is above address 19720h
This is a sample program that show what I mean
In this situation it works correctly. If I change to "@ ORG 19730h" it starts to do crazy things, reset, etc
Where can be the problem ?
    CONFIG  RETEN = ON          ; Enabled
    CONFIG  INTOSCSEL = LOW      ; LF-INTOSC in High-power mode during Sleep
    CONFIG  SOSCSEL = DIG        ;
    CONFIG  XINST = OFF           ; Disabled
    CONFIG FOSC = INTIO2        ; Internal RC oscillator
    CONFIG  PLLCFG = OFF           ; Enabled

    OSCCON        =110000                    ; Primary oscillator, internal 16MHz+PLL.
    OSCCON2.0    =1
    OSCTUNE.7    =1
    OSCTUNE.6    =1                            ' enable PLL -->> 64MHz
    Define         USE_LFSR     1
    DEFINE        OSC            64
    DEFINE        HSER2_RCSTA        90H
    DEFINE      HSER2_TXSTA      24H
    DEFINE         HSER2_BAUD        115200
    Led            VAR PORTB.3
    w0            VAR WORD
    goto pippo

@ ORG 19720h ' (does not work if I change to 19730h or above)
    random w0
    high led
    pause 150
    low led
    pause 150
    Hserout2["ORG " ,#w0,13,10]
    goto pippo